Circuit/System Description
WARNING: This page is about a different car, the 2009 GMC Sierra and 2009 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The engine control module (ECM) has 2 internal 5-volt reference busses called 5-volt reference 1 and 5-volt reference 2. Each reference bus provides 5-volt reference circuits for more than one sensor. Therefore, a fault condition on one 5-volt reference circuit will affect the other 5-volt reference circuits connected to that reference bus. The ECM monitors the voltage on the 5-volt reference busses.
The 5-volt reference 1 bus provides 5 volts to the following sensors:
- The manifold absolute pressure (MAP) sensor
- The fuel tank pressure (FTP) sensor
- The air conditioning (A/C) refrigerant pressure sensor
- The accelerator pedal position (APP) sensor 2
- The engine oil pressure (EOP) sensor
- The camshaft position (CMP) sensor
The 5-volt reference 2 bus provides 5 volts to the following sensors:
- The APP sensor 1
- The throttle position (TP) sensor 1 and 2
- The crankshaft position (CKP) sensor